U.S. patent application number 10/296651 was filed with the patent office on 2003-09-25 for sprayable coating compostion.
Invention is credited to Klinkenberg, Huig, Van Beelen, Jan Cornelis.
Application Number | 20030181625 10/296651 |
Document ID | / |
Family ID | 8171548 |
Filed Date | 2003-09-25 |
United States Patent
Application |
20030181625 |
Kind Code |
A1 |
Klinkenberg, Huig ; et
al. |
September 25, 2003 |
Sprayable coating compostion
Abstract
The present invention relates to a sprayable coating composition
comprising a) at least one isocyanate reactive compound comprising
at least one thiol group, b) at least one polyisocyanate functional
compound, and c) a catalyst comprising at least one organic metal
compound where the metal is a metal of Groups 3 to 13 of the
Periodic Table. The invention also relates to use of the sprayable
coating composition as a clear coat, its use as a clear coat, its
use as a clear coat in a multi-layer lacquer coating, and its use
in the refinish industry and in finishing large transportation
vehicles.
Inventors: |
Klinkenberg, Huig; (Katwijk
AAN ZEE, NL) ; Van Beelen, Jan Cornelis; (Katwijk,
NL) |
Correspondence
Address: |
Joan M Mcgillycuddy
Akzo Nobel Inc
Patent and Trademark Department
7 Livingstone Avenue
Dobbs Ferry
NY
10522-3408
US
|
Family ID: |
8171548 |
Appl. No.: |
10/296651 |
Filed: |
May 29, 2003 |
PCT Filed: |
May 23, 2001 |
PCT NO: |
PCT/EP01/05962 |
Current U.S.
Class: |
528/48 |
Current CPC
Class: |
Y10T 428/31551 20150401;
Y10T 428/31678 20150401; C08K 5/0008 20130101; C08G 18/792
20130101; C09D 175/04 20130101; Y10T 428/31605 20150401; C08G
18/4676 20130101; C08G 18/3876 20130101; C08G 18/222 20130101; C08K
5/0008 20130101; C08L 75/04 20130101 |
Class at
Publication: |
528/48 |
International
Class: |
C08G 018/08 |
Foreign Application Data
Date |
Code |
Application Number |
May 26, 2000 |
EP |
002018505 |
Claims
1. Sprayable coating composition comprising a) at least one
isocyanate reactive compound comprising at least one thiol group,
b) at least one polyisocyanate-functional compound, and c) a
catalyst comprising at least one organic metal compound where the
metal is a metal of Groups 3 to 13 of the Periodic Table.
2. Sprayable coating composition according to claim 1,
characterised in that the, metal is a transition metal.
3. Sprayable coating composition according to claim 2,
characterised in that the metal is a metal of Group 4 of the
Periodic Table.
4. Sprayable coating composition according to claim 1,
characterised in that the metal is selected from the group of
aluminium, titanium, zirconium, and hafnium compounds.
5. Sprayable coating composition according to any one of the
preceding claims, characterised in that the organic metal compound
is a metal complex.
6. Sprayable coating composition according to claim 5,
characterised in that the metal complexes comprise ligands selected
from the group of beta-diketones, alkyl acetoacetates, alcoholates,
and combinations thereof.
7. Sprayable coating composition according to any one of the
preceding claims, characterised in that a ketone based chelating
agent is added to the coating composition.
8. Sprayable coating composition according to any one of the
preceding claims, characterised in that at least 50% of the
isocyanate reactive groups are thiol groups.
9. Sprayable coating composition according to any one of the
preceding claims, characterised in that the isocyanate reactive
compound comprising at least one thiol group is derived from a
polyester compound.
10. Use of a coating composition according to any one of the
preceding claims, comprising applying the composition as a clear
coat.
11. Use of a coating composition according to claim 10, comprising
applying the composition as a clear coat in a multi-layer lacquer
coating.
12. Use of a coating composition according to any one of preceding
claims 1 to 9 in the refinish industry and in finishing large
transportation vehicles.
Description
[0001] The invention relates to a sprayable coating composition,
its use as a clear coat, its use as a clear coat in a multi-layer
lacquer coating, and its use in the refinish industry and in
finishing large transportation vehicles.
[0002] Coatings used for painting motor vehicles and repairing the
original paint are required to have good physical properties such
as hardness, mechanical strength, and resistance to water, acids,
and solvents. The coatings are also required to have good
appearance properties, which means that films must be smooth and
have a high gloss and a high distinctness of image. It is also
desirable that all properties are retained under prolonged outdoor
weathering.
[0003] For environmental reasons, it is required to use a coating
composition which can be applied easily using spray application at
a low volatile organic content (VOC). Coatings with a lower organic
solvent content emit lower levels of solvent when they are used,
and so the atmosphere becomes less polluted.
[0004] U.S. Pat. No. 4,788,083 discloses a sprayable coating
composition comprising a hydroxyl compound, an isocyanate, a metal
catalyst selected from tin and bismuth, and a molar excess of a
complexing agent such as a mercapto compound. Although tin and
bismuth catalysts are known metal catalysts for the hydroxyl
isocyanate reaction, it has been found that these metal catalysts
do not catalyse the thiol isocyanate reaction. Furthermore, the
mercapto compound in U.S. Pat. No. 4,788,083 is used to complex and
thus deactivate the metal catalyst. The activation of the metal
catalyst is effectuated by heat or the addition of a tertiary amine
activator. So, the reaction of hydroxyl isocyanate only starts when
the metal catalyst is activated.
[0005] The present invention relates to a sprayable coating
composition comprising
[0006] a) at least one isocyanate reactive compound comprising at
least one thiol group,
[0007] b) at least one polyisocyanate-functional compound, and
[0008] c) a catalyst comprising at least one organic metal compound
where the metal is a metal of Groups 3 to 13 of the Periodic
Table.
[0009] It has surprisingly been found that sprayable coating
composition can be provided where the thiol isocyanate reaction can
be catalysed in the presence of an organic metal compound, the
metal being a metal of Groups 3 to 13 of the Periodic Table, both
at room temperature and at higher temperatures such as 60.degree.
C. At all temperatures, an excellent pot life--drying balance is
shown. An additional advantage is the fact that there is no
necessity to add a tertiary amine activator to the coating
composition. This addition would have a negative effect on the pot
life of the coating composition. Furthermore, the sprayable coating
composition of the present invention provides excellent properties
such as were mentioned above to be necessary for its use in the
refinish industry and in finishing large transportation
vehicles.
[0010] Although we do not want to be bound by any theory, it is
suggested that the capacity of the organic metal compound to
hydrolyse plays a significant role in the reaction mechanism of the
thiol isocyanate reaction. Therefore, the reaction of thiol and
isocyanate compounds performs quite differently from the reaction
of hydroxyl and isocyanate compounds in the presence of metal
catalysts.
[0011] U.S. Pat. No. 5,849,864 discloses a sprayable coating
composition comprising a polymercapto resin, a polyisocyanate, and
a tin catalyst complex. The tin catalyst is complexed with
sulphonic acid. Upon exposure to an amine, the catalyst complex
becomes activated. It has been found that tin catalyst complexes do
not catalyse the thiol isocyanate reaction. Furthermore, as
mentioned above, it is a disadvantage to use amine in coating
compositions. WO 98/15585 discloses a sprayable coating composition
comprising a hydroxyl compound, an isocyanate, and a catalyst which
is the reaction product of a titanium, zirconium, hafnium or
aluminium ortho ester, a beta-diketone or beta-ketoester, and a
complexing agent such as a mercapto compound. The catalyst as such
can be used in the range of 0.005 to 0.5 per cent by weight with
respect to the weight of the reaction mixture. Although a mercapto
compound is present in the coating composition, this is in such
small quantities that WO 98/15585 does not disclose the coating
composition of the present invention.
[0012] JP-A-04-063823 discloses an architectural sealant comprising
a compound having two or more thiol groups per molecule, a
polyisocyanate compound, and a metallic soap. It is not disclosed
or suggested how to prepare a sprayable coating composition
thereof, nor is its use in a clear coat with the above-mentioned
properties described.
[0013] U.S. Pat. No. 5,064,871 discloses a composition comprising
an isocyanate reactive compound, a polyisocyanate, and a catalyst
comprising a bismuth and a zirconium carboxylate. Although the use
of polymercaptan as an isocyanate reactive compound is mentioned in
the description, only polyol resins are exemplified. Furthermore,
the composition is used in particular as an adhesive. It is not
disclosed or suggested how to prepare a sprayable coating
composition thereof, nor is its use in a clear coat with the
above-mentioned properties described.
[0014] U.S. Pat. No. 4,312,971 discloses a composition comprising
an organic compound comprising at least two active hydrogen atoms,
a polyisocyanate, and a catalyst comprising an organo zirconium and
an organo mercury compound. Although the use of aliphatic thiols as
an organic compound comprising at least two active hydrogen atoms
is mentioned in the description, only polyol resins are
exemplified. Furthermore, the composition is used in particular as
non-cellular polyurethanes, and cellular rigid and flexible
polyurethane foams. It is not disclosed or suggested how to prepare
a sprayable coating composition thereof, nor is its use in a clear
coat with the above-mentioned properties described.
[0015] JP-A-10182786 discloses a sealant comprising a polymer
having two or more thiol groups per molecule, a polyisocyanate
compound, and an organic metal. Although it is mentioned in the
description that organic mercury compounds and organic lead
compounds can be used, only organic tin compounds are exemplified.
As already mentioned before, tin does not catalyse the reaction of
thiol and isocyanate. Furthermore, in JP-A-10182876 it is not
disclosed or suggested how to prepare a sprayable coating
composition thereof, nor is its use in a clear coat with the
above-mentioned properties described.
[0016] The use of organic metal compounds, such as zirconium,
hafnium, and aluminium complexes, in the hydroxyl isocyanate
reaction is disclosed in Florio J., Paint & Coatings Industry,
Oct. 1997, pp. 110-120, and in U.S. Pat. No. 5,846,897. However, it
is not disclosed or suggested that these complexes may be used in
the thiol isocyanate reaction.
[0017] The catalyst comprises at least one organic metal compound
where the metal is a metal of Groups 3 to 13 of the Periodic Table.
Preferably, the metal is a transition metal. More preferably, the
metal is a metal of Group 4 of the Periodic Table.
[0018] The organic metal compounds comprise metal salts and/or
complexes of organic compounds. The organic compounds are groups
having 2 to 40 carbon atoms, optionally comprising atoms such as O,
N, and S. The metal salts comprise anions selected from the groups
of carboxylates. Examples thereof include propionate, butyrate,
pentanoate, 2-ethyl hexanoate, naphthenate, oxalate, malonate,
succinate, glutamate, and adipate. The metal complexes comprise
ligands selected from the group of beta-diketones, alkyl
acetoacetates, alcoholates, and combinations thereof. Examples
thereof include acetyl acetone (2,4-pentanedione),
2,4-heptanedione, 6-methyl-2,4-heptadione, 2,4-octanedione,
propoxide, isopropoxide, and butoxide. Preferably, the organic
metal compound is a metal complex.
[0019] Examples of metals include aluminium, titanium, zirconium,
and hafnium. Examples of metal complexes include aluminium
complexed with 2,4-pentanedione (K-KAT.RTM. XC5218 ex King
Industries), aluminium triacetyl acetonate, zirconium tetraacetyl
acetonate, zirconium tetrabutoxide (Tyzor.RTM. NBZ ex Dupont),
titanium tetrabutoxide (Tyzor.RTM. TBT ex Dupont), zirconium
complexed with 6-methyl-2,4-heptadione, K-KAT.RTM. XC6212 ex King
Industries, aluminium triisopropoxide, and titanium diisopropoxide
bis-2,4(pentadionate) (Tyzor.RTM. AA ex DuPont). These catalysts
may be used in an amount of 0.01 to 10 wt. % on solid curable
material, preferably 0.1 to 5 wt. %.
[0020] Examples of the isocyanate reactive compound comprising at
least one thiol group include a thiol-functional compound
comprising at least two thiol-functional groups and a compound
comprising at least one thiol-functional group and one
hydroxyl-functional group. Also mixtures of these compounds may be
used in the compositions of the present invention.
[0021] Suitable thiol group-containing compounds are generally
prepared by reacting hydroxyl group-containing compounds with thiol
group-containing acids, such as 3-mercapto propionic acid,
2-mercapto propionic acid, thio-salicylic acid, mercapto succinic
acid, mercapto acetic acid, or cysteine. Examples of suitable
hydroxyl group-containing compounds are diols, triols, and
tetraols, such as 1,4-butane diol, 1,6-hexane diol,
2,2-dimethyl-1,3-propane diol, 2-ethyl-2-propyl-1,3-propane diol,
1,2-, 1,3-, and 1,4-cyclohexane diols, and the corresponding
cyclohexane dimethanol, 1,1,1-trimethylol propane,
1,2,3-trimethylol propane, and pentaerythritol. Examples of
compounds prepared according to such a method include
pentaerythritol tetrakis (3-mercapto propionate), pentaerythritol
tetrakis (2-mercapto acetate), trimethylol propane tris (3-mercapto
propionate), trimethylol propane tris (2-mercapto propionate), and
trimethylol propane tris (2-mercapto acetate). Good results have
been obtained with trimethylol propane tris (3-mercapto propionate)
and pentaerythritol tetrakis (3-mercapto propionate).
[0022] A further example of a compound prepared according to such a
method consists of a hyperbranched polyol core based on a starter
polyol, e.g., trimethylol propane, and dimethylol propionic acid.
This polyol is subsequently esterified with 3-mercapto propionic
acid and isononanoic acid. These methods are described in European
patent application EP-A 0 448 224 and International patent
application WO 93/17060.
[0023] Other syntheses to prepare compounds comprising at least two
thiol-functional groups involve:
[0024] the reaction of an aryl or alkyl halide with NaHS to
introduce a pendent thiol group into the alkyl and aryl compounds,
respectively;
[0025] the reaction of a Grignard reagent with sulphur to introduce
a pendent thiol group into the structure;
[0026] the reaction of a polymercaptan with a polyolefin according
to a Michael addition reaction, a nucleophilic reaction, an
electrophilic reaction or a radical reaction;
[0027] the reaction of a polyisocyanate with a thiol-functional
alcohol, and
[0028] the reduction of disulphides.
[0029] The compound comprising at least one thiol-functional group
and one hydroxyl-functional group may for example have a structure
according to the following formula:
T[(C.sub.3H.sub.6O).sub.nCH.sub.2CHOHCH.sub.2SH].s- ub.3, with T
being a triol such as trimethylol propane or glycerol. An example
of such a compound is commercially available from Henkel under the
trademark Henkel Capcure.RTM. 3/800.
[0030] Alternatively, the isocyanate reactive compound comprising
at least one thiol group is a resin having as a backbone a
polyester resin, polyurethane resin, polyacrylate resin, and
polyether resin. These isocyanate reactive compounds may then also
comprise hydroxyl groups.
[0031] The isocyanate reactive compound comprising at least one
thiol group may be a polyester prepared from (a) at least one
polycarboxylic acid or reactive derivatives thereof, (b) at least
one polyol, and (c) at least one thiol-functional carboxylic acid.
The polyesters preferably possess a branched structure. Branched
polyesters are conventionally obtained through condensation of
polycarboxylic acids or reactive derivatives thereof, such as the
corresponding anhydrides or lower alkyl esters, with polyalcohols,
when at least one of the reactants has a functionality of at least
3.
[0032] Examples of suitable polycarboxylic acids or reactive
derivatives thereof are tetrahydrophthalic acid, tetrahydrophthalic
anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride,
methyl hexahydrophthalic acid, methyl hexahydrophthalic anhydride,
dimethylcyclohexane dicarboxylate, 1,4-cyclohexane dicarboxylic
acid, 1,3-cyclohexane dicarboxylic acid, phthalic acid, phthalic
anhydride, isophthalic acid, terephthalic acid, 5-tert. butyl
isophthalic acid, trimellitic anhydride, maleic acid, maleic
anhydride, fumaric acid, succinic acid, succinic anhydride,
dodecenyl succinic anhydride, dimethyl succinate, glutaric acid,
adipic acid, dimethyl adipate, azelaic acid, and mixtures
thereof.
[0033] Examples of suitable polyols include trimethylol propane,
trimethylol ethane, glycerol, 1,2,6-hexanetriol, ethylene glycol,
1,2-propylene glycol, 1,3-propylene glycol,
2-methylpropane-1,3-diol, neopentyl glycol,
2-butyl-2-ethyl-1,3-propane diol, cyclohexane-1,4-dimethylol, the
monoester of neopentyl glycol and hydroxypivalic acid, hydrogenated
Bisphenol A, 1,5-pentane diol, 3-methyl-pentane diol, 1,6-hexane
diol, 2,2,4-trimethyl pentane-1,3-diol, dimethylol propionic acid,
pentaerythritol, di-trimethylol propane, dipentaerythritol, and
mixtures thereof.
[0034] Examples of suitable thiol-functional organic acids include
3-mercaptopropionic acid, 2-mercaptopropionic acid, thio-salicylic
acid, mercaptosuccinic acid, mercaptoacetic acid, cysteine, and
mixtures thereof.
[0035] Optionally, monocarboxylic acids and monoalcohols may be
used in the preparation of the polyesters. Preferably,
C.sub.4-C.sub.18 monocarboxylic acids and C.sub.6-C.sub.18
monoalcohols are used. Examples of the C.sub.4-C.sub.18
monocarboxylic acids include pivalic acid, hexanoic acid, heptanoic
acid, octanoic acid, nonanoic acid, 2-ethylhexanoic acid,
isononanoic acid, decanoic acid, lauric acid, myristic acid,
palmitic acid, isostearic acid, stearic acid, hydroxystearic acid,
benzoic acid, 4-tert. butyl benzoic acid, and mixtures thereof.
Examples of the C.sub.6-C.sub.18 monoalcohols include cyclohexanol,
2-ethylhexanol, stearyl alcohol, and 4-tert. butyl
cyclohexanol.
[0036] Good results may also be obtained with an aqueous
thiol-functional polyurethane dispersion which is obtainable by
first preparing an isocyanate-functional polyurethane from diols,
diisocyanates, and building blocks containing groups which
facilitate the stabilisation of the resin in an aqueous dispersion,
followed by reaction of the isocyanate-functional polyurethane with
a polyfunctional thiol in a base-catalysed addition reaction,
followed by dispersion in water.
[0037] The isocyanate reactive compound comprising at least one
thiol group may be a thiol-functional polyacrylate. Such a
polyacrylate is derived from hydroxy-functional acrylic monomers,
such as hydroxy ethyl (meth)acrylate, hydroxy propyl
(meth)acrylate, hydroxy butyl (meth)acrylate, other acrylic
monomers such as (meth)acrylic acid, methyl (meth)acrylate, butyl
(meth)acrylate, optionally in combination with a vinyl derivative
such as styrene, and the like, or mixtures thereof, wherein the
terms (meth)acrylate and (meth)acrylic acid refer to both
methacrylate and acrylate, as well as methacrylic acid and acrylic
acid, respectively. The thiol group is introduced by the reaction
product of dimethyl-m-isopropenyl benzyl isocyanate and mercapto
ethanol. Alternatively, glycidyl methacrylate is introduced into
the polymer to prepare an epoxy-functional polyacrylate. The epoxy
groups are then reacted with suitable thiol-functional organic
acids such as mentioned above. The polyacrylate is prepared by
conventional methods, for instance, by the slow addition of
appropriate monomers to a solution of an appropriate polymerisation
initiator, such as an azo or peroxy initiator.
[0038] Also included in the coating compositions of the invention
may be di-, tri-, or higher thiol-functional diluents such as
ethane dithiol or bis-beta-mercapto-ethyl sulphide. Preference is
given to the use of higher-molecular weight thiol-functional
compounds, which may be obtained by reaction of a
polythiol-functional compound with a polyisocyanate.
[0039] Preferably, the isocyanate reactive compound comprising at
least one thiol group is derived from a polyester compound.
Examples thereof include the above-mentioned reaction product of
hydroxyl group-containing compounds with thiol group-containing
acids and the above-mentioned polyester prepared from (a) at least
one polycarboxylic acid or reactive derivatives thereof, (b) at
least one polyol, and (c) at least one thiol-functional carboxylic
acid. The most preferred thiol-functional compound is
pentaerythritol tetrakis (3-mercapto propionate).
[0040] The organic polyisocyanate includes polyfunctional,
preferably free polyisocyanates, with an average NCO functionality
of 2.5 to 5, and may be (cyclo)aliphatic, araliphatic or aromatic
in nature. The polyisocyanate may include biuret, urethane,
uretdione, and isocyanurate derivatives. Examples of these organic
polyisocyanates include 1,6-diisocyanatohexane, isophorone
diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate,
diphenyl methane-diisocyanate, 4,4'-bis(isocyanato-cyclohexyl)
methane, 1,4-diisocyanatobutane, 1,5-diisocyanato-2,2-dimethyl
pentane, 2,2,4-trimethyl-1,6-diisocyanatohe- xane,
1,10-diisocyanatodecane, 4,4-diisocyanato-cyclohexane,
2,4-hexahydrotoluene diisocyanate, 2,6-hexahydrotoluene
diisocyanate, norbornane diisocyanate, 1,3-xylylene diisocyanate,
1,4-xylylene diisocyanate, 1-isocyanato-3-(isocyanato
methyl)-1-methyl cyclohexane,
m-.alpha.,.alpha.-.alpha.',.alpha.'-tetramethyl xylylene
diisocyanate, the above-mentioned derivatives thereof, and mixtures
thereof. Normally, these products are liquid at ambient temperature
and commercially available in a wide range. Particularly preferred
isocyanate curing agents are triisocyanates and adducts. Examples
thereof are 1,8-diisocyanato4-(isocyanatomethyl) octane, the adduct
of 3 moles of toluene diisocyanate to 1 mole of trimethylol
propane, the isocyanurate trimer of 1,6-diisocyanatohexane, the
isocyanurate trimer of isophorone diisocyanate, the uretdione dimer
of 1,6-diisocyanatohexane, the biuret trimer of
1,6-diisocyanatohexane, the adduct of 3 moles of
m-.alpha.,.alpha.-.alpha.',.alpha.'-tetramethyl xylene diisocyanate
to 1 mole of trimethylol propane, and mixtures thereof. Preferred
are cyclic trimers (isocyanurates) and uretdiones of 1,6-hexane
diisocyanate and isophorone diisocyanate. Usually these compounds
contain small quantities of their higher homologues.
[0041] Optionally, a water borne coating composition according to
the present invention may also comprise an organic hydrophilic
polyisocyanate compound substituted with non-ionic groups, such as
C.sub.1-C.sub.4 alkoxy polyalkylene oxide groups. Preferably, 30
wt. % of non-ionic groups will be present on the total solid
polyisocyanate compound, more preferably 20 wt. %, most preferably
15 wt. %. Preferred are the isocyanurates of 1,6-hexane
diisocyanate and isophorone diisocyanate substituted with methoxy
polyethylene glycol.
[0042] Optionally, a hydroxyl-functional compound comprising at
least two hydroxyl-functional groups may be present in the curable
material. The hydroxyl-functional compound comprising at least two
hydroxyl-functional groups may be selected from polyester polyols,
polyether polyols, polyacrylate polyols, polyurethane polyols,
cellulose acetobutyrate, hydroxyl-functional epoxy resins, alkyds,
and dendrimeric polyols such as described in WO 93/17060. Also,
hydroxyl-functional oligomers and monomers, such as castor oil and
trimethylol propane, may be included. A preferred polyol is an
acrylate polyol. More preferred is an acrylate polyol available
from Akzo Nobel Resins having the trade name Setalux.RTM. 1157.
[0043] The polyisocyanate and the compound comprising isocyanate
reactive groups should be mixed such that the ratio of isocyanate
groups to isocyanate reactive groups is in the range of 0.5-3:1,
preferably 0.75-2.5:1, and more preferably 1-2:1. It is preferred
that at least 10% of the isocyanate reactive groups are thiol
groups, more preferred at least 25%, most preferred at least
50%.
[0044] If hydroxyl-functional compounds are present in the coating
composition, catalysts for the cross-linking of isocyanate groups
with hydroxyl groups may be present. Examples thereof include
Sn-based catalysts, such as dibutyl tin dilaurate and dibutyl tin
diacetate.
[0045] The polyisocyanate may be mixed with the isocyanate reactive
compound by any suitable technique. However, simply stirring
usually is sufficient. Sometimes it may be useful to dilute the
polyisocyanate somewhat with an organic solvent like ethyl acetate
or 1-methoxy-2-propyl acetate to reduce its viscosity.
[0046] Optionally, a ketone based chelating agent may be added to
the coating composition. Examples of these chelating agent include
beta-dicarbonyls, alpha-hydroxyl ketones, fused aromatic
beta-hydroxy ketones, dialkyl malonates, aceto acetic esters, alkyl
lactates, and alkyl pyruvates. Preferably, beta-dicarbonyls such as
acetyl acetone are used. The ketone based chelating agent may be
used in an amount up to 10 wt. % on solids, preferably up to 5 wt.
%.
[0047] The composition according to the present invention may be a
water borne composition, a solvent borne composition or a
solvent-free composition. Since the composition may be composed of
liquid oligomers, it is especially suitable for use as a high
solids composition or a solvent-free composition. Alternatively,
the coating composition of the present invention may be an aqueous
powder coating dispersion wherein the isocyanate reactive compound
comprising at least one thiol group has a Tg above 20.degree. C.
The coating composition may as well be used in powder coating
compositions and hot melt coatings compositions. Preferably, the
theoretical volatile organic content (VOC) in the composition is
less than about 450 g/l, more preferably less than about 350 g/l,
most preferably less than about 250 g/l.
[0048] The coating compositions may further comprise other
ingredients, additives or auxiliaries, such as pigments, dyes,
emulsifiers (surfactants), pigment dispersion aids, levelling
agents, anti-cratering agents, antifoaming agents, wetting agents,
antisagging agents, heat stabilisers, UV absorbers, antioxidants,
and fillers.
[0049] The coating composition of the present invention may be
applied to any substrate. The substrate may be, for example, metal,
plastic, wood, glass, ceramic, or some other coating layer. The
other coating layer may be comprised of the coating composition of
the current invention or it may be a different coating composition.
The coating compositions of the current invention show particular
utility as clear coats, base coats, pigmented top coats, primers,
and fillers. Preferably, the coating composition according to the
present invention may be used as clear coat or as primer.
[0050] The coating compositions can be applied by conventional
means such as by spray gun, brush, or roller, spraying being
preferred. Curing temperatures preferably are between 0 and
100.degree. C. and more preferably between 20 and 60.degree. C. The
compositions are particularly suitable in the preparation of coated
metal substrates, such as in the refinish industry, in particular
the body shop, to repair automobiles and transportation vehicles,
and in finishing large transportation vehicles such as trains,
trucks, buses, and aeroplanes.
[0051] The composition of the present invention is also suitable
for application by an external mixing apparatus, one where a liquid
composition comprising at least one isocyanate-functional compound
and at least one isocyanate reactive compound is sprayed via a
spray nozzle, with a small amount of catalyst. Such an apparatus is
described, for example, in WO 98/41316. Due to the very effective
use of the catalysts, the compositions according to the present
invention have very short curing times, which makes this method
specifically suitable for these compositions.
[0052] In the case of the coating composition being a clear coat,
the base coat may be a conventional base coat known in the coating
art. Examples are solvent borne base coats, e.g., Autobase.RTM. ex
Akzo Nobel Coatings BV, based on cellulose acetobutyrate, acrylic
resins, and melamine resins, and water borne base coats, e.g.,
Autowave.RTM. ex Akzo Nobel Coatings BV, based on an acrylic resin
dispersion and polyester resin. Furthermore, the base coat may
comprise pigments (colour pigments, metallics and/or pearls), wax,
solvents, flow additives, neutralising agent, and defoamers. Also
high solids base coats can be used. These are, for instance, based
on polyols, imines, and isocyanates. The clear coat composition is
applied to the surface of a base coat and then cured. An
intermediate curing step for the base coat may be introduced.
[0053] The invention will be illustrated with reference to the
following examples. Of course these examples are submitted for a
better understanding of the invention only; they are not to be
construed as limiting in any manner the scope thereof.
EXAMPLES
[0054]
1 List of abbreviations: Penta(SH)4 pentaerythritol tetrakis
(3-mercapto propionate) Other compounds used Tolonate .RTM. HDT-LV
ex Rhodia isocyanurate of hexamethylene diisocyanate Byk .RTM. 306
ex Byk Chemie levelling agent Tyzor .RTM. NBZ ex Dupont zirconium
tetrabutoxide (80 wt.% in n- butanol) Tyzor .RTM. TBT ex Dupont
titanium tetrabutoxide K-KAT .RTM. XC5218 ex King Industries
aluminium complexed with 2,4- pentanedione K-KAT .RTM. XC6212 ex
King Industries zirconium complex K-KAT .RTM. 348 ex King
Industries bismuth carboxylate 2-ethyl hexanoic acid
Methods
[0055] A coating is cured when the mark from firm pushing with the
thumb does not leave any imprint.
[0056] The gelling time was determined visually and is the time
after which the composition is no longer influenced by gravity.
Examples 1 to 11 and Comparative Examples A and B
[0057] A formulation was prepared comprising the following
compounds:
2 Penta(SH).sub.4 50 ToIonate .RTM. HDT LV 90 Byk 306(10 wt.% in
butyl acetate) 7,0
[0058] To this formulation were added several organic metal
compounds, optionally in combination with acetyl acetone (acac). A
50 .mu.m thick film was drawn out onto tin plated metal. The drying
time was evaluated at room temperature (RT) and at 60.degree.
C.
3 Wt. % Wt. % catalyst on solid acac added on binders catalyst Gel
time drying RT drying 60.degree. C. 1 1% K-KAT .RTM. XC5218 --
>1 day 1 hr 18 min. 2 3% K-KAT .RTM. XC6212 -- >1 day 45 min.
15 min. 3 0.5% Tyzor .RTM. NBZ -- 20 min. 15 min. 2 min. 4 0.5%
Tyzor .RTM. NBZ 500% >1 day 25 min. 5 min. 5 0.5% Tyzor .RTM.
NBZ 900% >1 day 35 min. 7 min. 6 0.5% Zr(acac).sub.4* -- 10 min
6 min. 3 min. 7 0.5% Zr(acac).sub.4 100% 1 day 10 min. 4 min. 8
1.5% Tyzor .RTM. TBT -- 35 min. 20 min 4 min 9 0.5% Tyzor .RTM. TBT
100% >1 day 75 min. 20 min 10 0.5% Al(iPrO).sub.3** -- 6 min 11
min 4 min 11 0.5% Al(acac).sub.3*** -- >1 day 210 min 25 min A
1% K-KAT .RTM. 348 -- >>1 h B 1% dibutyl tin dilaurate --
>>1 h *zirconium tetraacetyl acetonate **aluminium
triisopropoxide ***aluminium triacetyl acetonate
[0059] These examples show that organic metal compounds where the
metal is a metal of Groups 3 to 13 of the Periodic Table, such as
zirconium, aluminium, and titanium compounds, are very active
catalysts in the reaction between thiol and isocyanate. Their
results, optionally in combination with acetyl acetone, show an
excellent pot life/drying balance. Well-known catalysts for the
reaction between hydroxyl and isocyanate like dibutyl tin dilaurate
or bismuth carboxylate 2-ethyl hexanoic acid show no activity at
all.
* * * * *